Magnetic core structures



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CDQPDDCD/ Aug. 17, 1965 INVENTOR Roy L. Brown BY ATTORNEY WITNESSES United States Patent O (BRE STRUCTURES Pa., assiguor to Westinghouse East Pittsburgh, Pa., a corpra= This invention relates to electrical inductive apparatus, such as transformers, and more particularly, to magnetic core structures for such apparatus.

Because the trend in the voltage and kva. ratings of larger power transformers is increasingly higher, certain problems arise which relate to the shipping limitations on the maximum size and weight of such equipment. In order to overcome the latter limitations, it would be advantageous to employ magnetic cores of the shell form type in certain applications of large power transformers. The use of certain conventional magnetic cores of the shell form type, which include a plurality of assembled layers of laminations of magnetic material, is limited however because of the cooling problem which results during the operation of such apparatus due to the width of the laminations included in such magnetic cores. It is therefore desirable to provide improved core structures of the shell form type for large power transformers which overcome the latter cooling problem and which also provide additional advantages as well. v

It is an object of this invention to provide a new and improved magnetic core structure of the shell form type for electrical inductive apparatus.

Another object of this invention is to provide a new and improved cooling arrangement for magnetic core structures.

A more speciiic object of this invention is to provide a new and improved three-phase magnetic core structure of the shell form type for transformers which lends itself to more efficient cooling by an associated cooling medium.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

FiGURE l is a plan view of a three-phase magnetic core structure embodying the teachings of the invention;

FIG. 2 is a plan view of a single phase magnetic core structure embodying the teachings of the invention; and

FIG. 3 is a partial sectional view illustrating a modication of the magnetic core structure shown in FIG. 1.

Referring now to the drawing and FIG. l in particular, there is illustrated a core and coil assembly including the three-phase magnetic core structure 1t) and the three-phase electrical windings 29A, 20B and 20C, which are inductively disposed thereon. In general, the magnetic core 1G which is substantially rectangular in its overall configuration and is of the five-legged type comprises a plurality of stacked or assembled layers of laminations which form a plurality of yoke and leg members assembled around four substantially rectangular windows. The laminations which make up the magnetic core 1li are preferably formed from a suitable magnetic strip or sheet material having at least one preferred direction of orientation or direction of easier magnetization substantially parallel to its edges or longitudinal dimensions, such as cold rolled silicon steel.

In particular, each layer of laminations of the magnetic core 1t) includes the first and second outer leg laminations 62 and 72, respectively, the first, second and third intermediate or inner leg laminations 64, 66 and 3,2il,73,3 Patented Aug. 17, 1965 ICC 68, respectively, the first, second, third and fourth yoke laminations 32, 34, 36 and 3S, respectively, at one end of the magnetic core 1t) and the first, second, third and fourth yoke laminations 42, 44, 46 and 4S, respectively, at the other end of the magnetic core 10. As shown in FIG. l, the outer leg laminations 62 .and 72 and the intermediate ieg laminations 64, 65 and 65 are spaced apart from one another and disposed substantially parallel to one another with the ends of the respective leg laminations being connected by the associated yoke laminations to form closed magnetic paths or loops in the different portions of the magneic core 1t) and to provide the four substantially rectangular windows, previously mentioned, through which the conductor turns of the associated windings 26A, 26B and 243C pass. It is to be noted that the width of the intermediate leg laminations 64, 66 and 68 must be substantially twice the width of the outer leg laminations 62 and 72 and the associated yoke laminations, since the magnitude of the magnetic liux which must be carried by said intermediate leg laminations during the operation of the transformer core and coil assembly which includes the magnetic core it? is substantially twice as great as the magnitude of the magnetic flux which must be carried by the balance of the laminations in each layer of the magnetic core it?.

Both ends of the first outer leg lamination 62 are cut at an oblique angle, preferably at an angle of substantially 45 with respect to the direction of orientation of the strip material from which said lamination is formed, while both ends of the second outer leg lamination 72 are cut at substantially a right angle or 90 with respect to the preferred direction of orientation of the strip material from which the latter lamination is formed. Both ends of each of the intermediate leg laminations 64, 66 and 68 are also cut diagonally or at an oblique angle with respect to the preferred direction of orientation of the strip material from which said laminations are formed in a generally trapezoidal configuration. One end of each of the yoke laminations 32 through 38 and 42 through 4S is cut at an oblique angle with respect to the direction of orientation of the strip material from which said laminations is formed, as indicated at 133 through 136 and 142 through 145, respectively, while the other end of each of said yoke laminations is cut at substantially a right angle with respect to said direction of orientation, as indicated at 137 through 146 and 146 through 149, respectively. It is to be noted that the diagonally cut ends of each of the yoke laminations 32 and 42 are preferably cut at an angle of substantially 45 with respect to the direction of orientation of the strip material from which said laminations are formed to match the ends of the associated leg laminations. It is also to be noted that the meeting ends or edges of the outer laminations 64, 66 and and 72 and the intermediate leg laminations 64, 66 and 68 and the associated yoke laminations abut one another with the joints between the outer leg lamination 62 and the associated yoke laminations and the joints between the intermediate leg laminations 64, 66 and 68 and the associated yoke laminations being diagonal joints or substantially mitered or beveled joints in which the magnetic iiux iiows between the different laminations in substantially a continuous straight line which substantially coincides with the most favorable direction of orientation of the strip material from which said laminations are formed. The overall reluctance of the magnetic core itl is therefore reduced by the increased length or effective cross-sectional area of the diagonal joints between the leg laminations and the associated yoke laminations just described.

During the stacking or assembling of the layers of the result in a lower reluctance in the magnetic core 10. For

example, the joints between the outer leg lamination 62 .andthe associated yoke laminations 32 and 42 as indicated at 133 and 142, respectively, are displaced from the joints between the corresponding outer leg and yoke laminations in the adjacent layer, as indicated by the joints 171 and 131, respectively, to provide an area of overlap therebetween. Similarly, the joints between the outer leg laminations 72 and the associated yoke laminations Se and 48, as indicated at 140 and 149, respectively, are displaced from the joints between the corresponding outer leg and yoke laminations in the adjacent layer as indicated iat 167 and 188, respectively, to provide an area of overlap therebetween. The diagonal joints between the upper ends of the intermediate leg laminations 64, 66 and 68 and the associated yoke laminations as indicated at 134, 135 and 136, respectively, are disposed oppositely to the `joints between the correspondingintermediate leg and yoke laminations in the adjacent layer as indicated at 164, 165 and 166, respectively, to provide an area of overlap therebetween. Similarly, the diagonal joints between the lower ends of the intermediate leg laminations 64, 66 and 68 and the associated yoke laminations as indicated at 143, v144i and 145, respectively, are also disposed oppositely with respect to the diagonal joints between the corresponding intermedi-ate leg and yoke laminations in the adjacent layer as indicated at 185, 186 and 187, respectively, to provide an area of overlap therebetween. It is to be understood that groups of three or more laminations ofthe same shape may be stacked or assembled simultaneously with alternate groups being reversed during stacking in a magnetic core as disclosed.

In order to more effectively cool the central portion of each of the intermediate leg laminations 64, 66 and 68, whose width is substantially twice the width of the associated outer yoke and leg laminations, during the operation of the core and coil assembly which includes the magnetic core 1i?, each of the intermediate leg laminations 64, 66 and 68 includes a plurality of perforations or holes which are disposed in the central portion of each of the intermediate leg laminations 64, 66 and 63, as best shown in FIG. 1. The perfo-rations or holes 52 in each of the intermediate leg laminations 64, 66 and 63 are spaced apart from one another along a central axis of each of said intermediate leg laminations. During the assembly or stacking of each of the intermediate leg laminations 64 66 and 68 of the magnetic core 10, the perforations or holes 52 in each of said intermediate leg laminations are substantially aligned or disposed in substantial registry with the perforations or holes in the adjacent layers of laminations to provide one or more passageways for an associated cooling medium to pass through the central portion of each ofthe intermediate leg laminations 66, 64 and 68. As indicated by the arrow for intermediate leg laminations 64 in FIG. 3, the cooling medium williiow in an upward direction due to Vthermosiphon or pump action through the openings or holes 52. The latter ilow of a cooling medium through the holes or perforations 52 more etiiciently carries off the heat which results in the central portion of each or" the intermediate leg laminations 64, 66 .and 68, which would otherwise have to flow by conduction to the outer edges of each of said intermediate leg laminations through a distance which is substantially twice as great as the corresponding distance in each of the associated outer leg and yoke laminations. In other words, the perforations or holes 52 in each of the intermediate leg laminations 6d, Y66 and 68 provide one or more cooling ducts in'each of said intermediate leg laminations through which an associated cooling medium may iiow vertically through said laminations.

Referring now to FIG. 3, there is illustrated an alternate construction of the magnetic core 1@ in which the respective intermediate leg laminations 64, 66 and 68 are bonded together in order to maintain -said intermediate leg laminations in predetermined positions with respect to the associated windings 26A, 29B and 26C, respectively, after the magnetic core 16 is assembled with said windings to form the core and coil assembly shown in FlG. l. As illustrated for the intermediate leg laminations 64 in FlG. 3, a suitable thermosetting resin, such as an epoxy resin, as indicated at 65, is disposed between said intermediate leg laminations to bond them together in a substantially unitary member. ln order to permit the assembly or interleaving of the associated Vyoke laminations with the ends of each of the intermediate leg laminations 64, 66 and 66, each of said intermediate leg laminations may be coated on at least one side thereof only in the portion of each of said intermediate leg laminations between the associated yoke laminations as assembled. The thermosetting resin 65 may be then cured in place by any suitable means, such as a heat treatment. The construction just described has the advantage that it eliminates the need for a separate supporting member or means, such as a T-beam, which is employed in certain conventional magnetic cores of the shell form type.

Referring to FIG. 2, there is illustrated a second embodiment of the invention in a core and coil assembly which includes a single phase magnetic core 260 of the shell form type and an associated electrical winding 226 which is inductively disposed on said magnetic core. In general, the magnetic core 260 is similar to the magnetic core 10 except that each layer of laminations of the magnetic core 260 includes only one intermediate leg lamination rather than three intermediate leg laminations as in the magnetic core 10 and the magnetic core 200 includes only two substantially rectangular windows rather than tour substantially rectangular windows as in the magnetic core 1t).

ln particular, the magnetic core 26S comprises a plurality of assembled or stacked layers of laminations assembled around two substantially rectangular windows to form a substantially rectangular core as shown in FIG. 2. Each of the layers of llaminations of the magnetic core 260 include the irst and second outer leg laminations 262 and 266, respectively, the intermediate leg lamination 264, the yoke laminations 232 and 234 at one end of the magnetic core 261B and the yoke laminations 242 and 244 at the other end of the magnetic core 209, said yoke laminations connecting the ends -of the'associated leg laminations to Storm the closed magnetic paths or loops in the different portions of the magnetic core 200. v

Similarly to the magnetic core 1t), the laminations which make up the successive alternate layers of the magnetic core 266 are reversed during stacking to provide an area of overlap between the joints of the corresponding laminations in alternate layers. More specitically, both ends of the outer leg laminations 262 are cut at an oblique angle, preferably at an angle of substantially 45 with respect to the preferred direction of orientation of the magnetic strip material from which said laminations are formed, while both ends of the outer leg laminations 266 are cut at substantially a right angle with respect to said direction of orientation. Both ends of the intermediate leg laminations 264 are cut at an oblique angle with respect to the direction of orientation of the strip material from which said laminations are formed, while one end of each of the yoke laminations 2352, 234, 242 yand 244 is cut at an oblique angle to match the meeting end .of the associated leg laminations and form substantially mitered or beveled joints therewith similarly to the magnetic core 10. The other end of each of the yoke laminations 232, 234, 242 and 244 is cut at substantially a right angle with respect to the preferred direction of orientation of the strip material from which said yoke laminations are formed. The joints between the outer leg lamination 252 and the associated yoke laminations are overlapped by the laminations in the adjacent alternate layers as indicated at 284 .and 296 and 276 and 28g, respectively. Similarly, the joints between the outer leg laminations 266 and the associated yoke laminations are overlapped by the laminations in the adjacent alternate layers as indicated at 286 and 293 and 278 and 292, respectively. Since the intermediate leg laminations 264 are reversed in alternate layers during stacking, the joints between each of said intermediate leg laminations and the associated yoke laminations are overlapped by the laminations in the adjacent alternate layers as indicated at 252 and 274 and 232 and 294, respectively.

Similarly to the magnetic core 10, the intermediate leg laminations 2&4 of the magnetic core 200 include a plurality of perforations or apertures 254 in the central portion thereof. The perforations or holes 254 are disposed in spaced relationship along a central axis of the intermediate leg laminations 264 and the perforations of the different intermediate leg laminations 264 are substantially aligned or disposed in substantial registry during stacking or assembly to provide vertical passageways or cooling ducts to permit the liow of a cooling medium therethrough similarly to the magnetic core previously described. The magnetic core 200 therefore possesses the same advantages as the magnetic core 10 with respect to the more efficient cooling arrangement which is provided for the intermediate leg laminations.

It is to be noted that in the magnetic core 10 and the magnetic core 200 as disclosed, both ends of one outer leg lamination in each layer are cut at an oblique angle with respect to the direction of orientation of the strip material from which said lamination is formed while the other outer leg lamination of each layer has both ends cut at substantially a right angle with respect to the preferred direction of orientation. It is to be understood that in certain applications, each outer leg lamination of the magnetic core 10 and the magnetic core 200 may be modified to include one end which is cut at substantially a right angle and one end which is cut at substantially 45 With respect to the direction of orientation of the strip material from which said laminations are formed in order to reduce the number of lamination shapes required in said magnetic cores. In the latter modified forms of the magnetic cores i0 and 200, the shape of each of the intermediate leg laminations would also have to be modiled to be substantially a parallelogram in conliguration rather than being trapezoidal in configuration as in the magnetic cores l0 and 200. In other words, the ends of each of the intermediate leg laminations of each of the magnetic cores l0 and 200 would have to be cut at the Same Oblique angle with the ends of each of said intermediate leg laminations meeting the associated yoke laminations being substantially parallel.

It is also to be understood that the laminations which make up each of the magnetic cores 10 and 200 may also be formed from other suitable types of magnetic material, such as sheets of silicon-iron and aluminum-iron alloys containing from 1 to 7% silicon and from 1 to 10% aluminum, respectively, the sheets of said alloys having grains whose crystal lattice structure comprises four cube edges perpendicular to the plane of the sheet, known as cube texture, either doubly oriented or randomly oriented. The major volumetric proportion of the sheets is composed of grains having a crystalline lattice structure such that a cube face lies substantially parallel to the surface of the sheet and in the doubly oriented material,rfour cube 6 edges of the cube lattice are parallel to the rolling direction or edge of the sheet and four cube edges are transverse thereto. In the randomly oriented cube texture material, the grains may have eight cube edges randomly distributed parallel to the surface of the sheet. One such doubly oriented cube textured silicon iron alloy is that disclosed in copending application Serial No. 681,333, iiled August 30, 1957 and in copending application Serial No. 19,440 filed April 21, 1960 which are both assigned to the same assignee as the present application.

The apparatus embodying the teachings of this invention has several advantages. For example, a magnetic core as disclosed offers the advantages of reduced size and weight ot a shell form type magnetic core and provides more eliicient cooling for the magnetic core structure. In addition, the lamination shapes employed may be provided by substantially scrapless methods from magnetic strip material. Finally, in one modied form of the invention, the need for separate supporting members or means is eliminated as compared with certain types of conventional magnetic cores of the shell from type.

Since numerous changes may be made in the abovedescribed apparatus and dilerent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in ya limiting sense.

I claim as my invention:

A magnetic core comprising a plurality of stacked layers of laminations formed from magnetic material, said stacked layers forming first and second outer leg members, .at least one intermediate leg member, and yoke members connecting the ends of said leg members, the ends of the laminations in each of said stacked layers being cut at predetermined angles, said leg members being disposed substantially parallel to and spaced apart from one another .and assembled with the cuts on the ends of the leg laminations meeting matching cuts on the ends of the laminations in said yoke members to form a substantially rectangular core, the joints formed between the meeting matched cuts being overlapped by the laminations in adjacent layers, and bonding means, said bonding means being disposed between the plurality of layers of laminations which form said intermediate leg member, in the portion of said intermediate leg member which is disposed intermediate the associated yoke members, to bond the laminations which form said intermediate leg member into a substantially unitary member.

References Cited bythe Examiner UNITED STATES PATENTS 1,546,885 6/25 Burnham 336-60 2,137,433 11/38 Wirz 336-5 XR 2,494,180 1/50 Koubek 336-219 XR 2,554,262 5/51 Nagel 154-43 2,922,972 1/ 60 Gordy 336-5 XR 3,064,220 11/62 Specht 336-217 3,077,570 2/ 63 Popa 336-60 FOREIGN PATENTS 1,005,625 4/57 Germany.

699,549 11/53 Great Britain.

127,691 3/50 Sweden.

JOHN F. BURNS, Primary Examiner. MILTON O. HIRSHFIELD, Examiner. 

